Seasonal changes in the hatchability of Aedes albopictus eggs of Okinawajima, Japan, was studied for a year in the field and the laboratory. The eggs laid in the period from mid-October to December were apparently different physiologically from those laid in January to September. Some of the embryonated eggs laid in mid-October did not hatch for 2 months of submersion period. As the photoperiod became short, hatchability was apparently low and it became clear that there were some diapause eggs laid in the period from mid-October to December.

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The relationship between larval density of Anopheles sundaicus Edwards and several environmental factors was examined by 215 data which were obtained from April to June, 1982 in 38 ponds in a coastal village of North Sumatra, Indonesia. The data were analyzed by the quantification theory type I method. Density of the larvae was higher in the waters where fish were scarce, salinity was 0.5-0.8%, and/or the surface received much sunlight. Water salinity was most contributive to the density, followed by fish-abundance and sunlight condition. These three factors altogether contributed to 21% of total variance of the density. The contribution of fish-abundance suggested suppressive effect of predatory fish against the larvae in the field. Larval density of anopheline species other than An. sundaicus (mostly An. hyrcanus group) was much lower than that of An. sundaicus. When compared within other Anopheles group, the density was a little higher where water depth was greater (81-100cm), salinity was less than 0.4%, transparency was higher, and/or bloom of fibrous floating algae was luxuriant. Water depth was most contributive, followed by salinity, algal abundance and transparency. Contribution of these four factors altogether was 15% of total variance of the density.

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Fifteen d-cyphenothrin-treated sound traps were set in a 2-ha orchard at Gertak Sanggol village in Penang, Malaysia, from August 5 to 18,1989,to determine the effect on an Aedes albopictus population. When the population size was estimated at pre- and posttreatment by the mark-and-release method and adhesive sound traps, 80.9% of females and 75.6% of males were found to be controlled from the field. Meanwhile, there was little change in the mosquito catches by an adhesive sound trap at an untreated area. The insemination rate of females sampled by net sweeping increased from 57 to 100% as more females were removed than males. Necessity of a middle-distance attractant was suggested to raise the efficacy of traps.

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Trapping of both sexes of mosquitoes achieves more efficient control than manipulating the male population. For this purpose, various chemical and physical stimuli known to be attractive were reevaluated. Heat, black color, L-lactic acid, movement and sound were all attractive to both sexes of Aedes aegypti when tested individually under laboratory conditions. Black color, heat and lactic acid in this order contributed their attractancy in combinations with the other stimuli. In field tests at the fringe of a forest, however, only heat and sound proved to be of significant attractancy for female and male of Aedes albopictus, respectively. From these tests, it was suggested a powerful attractant from human emanations and optokinetic stimulus was necessary for further improvement of mosquito traps.

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Some factors that affect the occurrence and termination of quiescence in nymphs of Dermatophagoides farinae, were examined. The mites aggregating on the rims and covers of culture bottles were collected when the mite populations were increased. They were kept at 25℃, 75% relative humidity (RH), without food. After 1 month, about 20% of the mites passed into quiescent state, and a half of them remained quiescent for 5 months at 25℃, 75% RH, and further 5 months at room temperature. Most of the quiescent mites were protonymphs. They were glued to the substrate such as covering filter paper. Quiescence in half of the 8-week-aged nymphs terminated when they were disturbed by being separated from the substrate, pretreated at 5℃ for 1 week, and then incubated at 25℃, 75% RH. But the nymphs did not moult by pretreatment of 10,18,and 25℃ for 1 week. The nymphs in age of 20-week or more moulted even when they were continuously incubated at 25℃ and 75% RH, if separation from the substrate was made. The moulting rates depended on age in the nymphs; the older the nymphs, the faster the moulting. However, the nymphs glued onto the substrate remained quiescent. Moulting of nymphs with age of 22-week or more was suppressed by incubating them at lower temperatures than 25℃, or lower than 55% RH. The contact of the quiescent nymphs with water for 3hr enhanced moulting even when they were incubated at 33% RH. These results suggest that quiescence in nymphs of D. farinae observed in the present study might also involve a very similar phenomenon to diapause.

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An epidemiological survey on the vector mites of Tsutsugamushi disease was conducted in Taiwan and the Ryukyu Islands. On the Penghu Islands and Taitung of Taiwan, the only trombiculid mite belonging to the subgenus Leptotrombidium collected from rodents and insectivores was L. (L.) deliense, the potential vector of Rickettsia tsutsugamushi in the Asia-Pacific region south of Japan. On the other hand, on Mt. Alishan three species of the subgenus Leptotrombidium including L. (L.) kawamurai were collected from rodents, suggesting that the reservoirs of R. tsutsugamushi may be in this highland. On Okinawa Island, Japan, the trombiculid mite was not collected from rodents and insectivores in the present survey.

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Mosquitoes were collected by light traps at a pigstay near paddy fields in Kochi, Japan, during 9 years from 1966 to 1974 and 8 years from 1982 to 1989. Major species were Culex tritaeniorhynchus (77.6%), Anopheles sinensis (7.0%) and Cx. pipiens pallens (15.4%) in 1966. However, the population size was gradually reduced especially in latter two species in recent 1980s. Cx. tritaeniorhynchus was caught through the end of March to mid-October, and it showed a peak of occurrence in June and July in 1966 and subsequent several years. Six larval generations were estimated in a year. A high degree of correlation was observed between the number of Cx. tritaeniorhynchus collected from May to September during 1966 and 1973 and the total area of rice fields or the proportion of two-crop fields in Kacho Plain in this period. There was, also, a high correlation coefficient (r=0.949) between the number of vector mosquitoes collected and the number of Japanese encephalitis patients in Kochi Prefecture during the same period. The number of vector mosquitoes caught by light traps decreased abruptly from the end of August even when the temperature is around 25℃. This phenomenon was partly explained from the results of laboratory experiments in which phototaxis and blood feeding behavior of adult females were suppressed when the larvae were bred under day length of 10hr or less at 20 or 25℃. The vector mosquito was not found in caves and other places in Kochi Prefecture throughout the winter surveys. Japanese encephalitis virus was not isolated from three other species than Cx. tritaeniorhynchus collected in winter.

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Control efficacy of an agricultual acaricide, pyridaben, against three kinds of mite, Cheyletus malaccensis, Dermatophagoides farinae, and Tyrophagus putrescentiae, was evaluated by the filter paper contact method and the medium mixing method. Pyridaben is highly effective to C. malaccensis by the filter paper contact method. It killed C. malaccensis completely at a dose of 25mg/m^2. Pyridaben gave 100% mortality to D. farinae and T. putrescentiae at a dose of 100 and 200mg/m^2,respectively. By the medium mixing method, pyridaben kept more than 98% suppression of population growth against D. farinae at 100ppm during 6 weeks. The chemical was, however, relatively less active to T. putrescentiae by the medium mixing method. It showed 81.8% suppression of population growth against T. putrescentiae at a dose of 250ppm.

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A new species, Sphaerocera elephantis, is described from Thailand. The genus is recorded from Southeast Asia for the first time.

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The prey-predator relationship between larvae of the mosquito Anopheles sinensis and nymphs of the dragonfly Sympetrum frequens in rice field areas was investigated in the suburbs of Omiya City, Japan, during the period from June to July of 1979 (for Area-A and the whole area) and 1980 (for Area-B), and July 1986 (for the whole area). The average density of S. frequens nymphs in Area-A (210a) and Area-B (430a) was 23-41/m^2 and 2-6/m^2,respectively. On the contrary, densities of An. sinensis larvae were very low in Area-A and high in Area-B. In both the areas, the density of S. frequens nymphs in a rice field was much different from those in neighbors. The precipitin test of the gut content of S. frequens nymphs with antiserum against An. sinensis larvae indicated that the proportion of An. sinensis larvae preyed by S. frequens nymphs was estimated to be 83.3 to 100% in Area-A and 0 to 87.5% in Area-B. The density of S. frequens nymphs in the whole area (97ha) was about 4/m^2 during the first half of June of 1979 and 1986. The distribution of nymphs in the area was contagious. On 17 June 1979,18.2% of S. frequens nymphs had detectable An. sinensis antigen in the gut, and 39% of An. sinensis larvae were estimated to be preyed by S. frequens nymphs during the day. An. sinensis larvae in the survey area could be controlled effectively by S. frequens through appropriate management of rice fields.

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[in Japanese]

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The distribution of larvae of Hirosia iyoensis was surveyed at the forest floor along a small branch of the Oyabe River of Toyama Prefecture. A total of 129H. iyoensis larvae was collected from leaf litter and soil at six different stations within 200m of the blood-sucking sites (a wide space opened at the main course of the Oyabe River) for H. iyoensis. Most of the larvae were collected within an 80m area of the blood-sucking sites. A total of 102 larvae was also collected at four stations with different altitudes (5,25,50 and 75m above the surface of the stream). The number of larvae collected tend to decrease in accordance with the elevation. This survey suggested that the breeding-places of larvae of H. iyoensis were the forest floor near the bloodsucking site of adults.

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A 57-year-old woman experienced pain from foreign bodies in her oral cavity after eating raw squid. Examination of her oral cavity revealed 20-30 small foreign bodies embedded in the mucous membrane. After all the foreign bodies were pulled out, the pain was allayed and the wounds eventually healed. The foreign bodies, 5mm in length, were white and of elongated conical shape. Under microscopy, a large number of sperms was observed in the bodies. These foreign bodies were determined to be sperm-bags of the squid. It is supposed that this woman ate squid with spermatophores, thereafter sperm-bags were discharged from the spermatophores into her oral cavity. Although only a few similar cases heretofore have been found, it might increase among the Japanese who frequently eat raw squid.

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